gentoo-overlay/metadata/news/2019-09-11-cpu_flags_ppc-introduction/2019-09-11-cpu_flags_ppc-introduction.en.txt

Title: new CPU_FLAGS_PPC USE_EXPAND
Author: Georgy Yakovlev <gyakovlev@gentoo.org>
Posted: 2019-09-11
Revision: 2
News-Item-Format: 2.0
Display-If-Keyword: ~ppc
Display-If-Keyword: ~ppc64
Display-If-Keyword: ppc
Display-If-Keyword: ppc64


A new set of CPU_FLAGS_PPC USE_EXPAND flags has been added.
The flags are:

  altivec - Use the AltiVec/VMX instruction set
  vsx - Use the Vector Scalar Extension instruction set
  vsx2 - Use the Vector Scalar Extension v.2 instruction set
  vsx3 - Use the Vector Scalar Extension v.3 instruction set

Note that CPU_FLAGS_PPC variable is used on ppc and ppc64 architectures.

In order to transition to new set of flags, if the following flag was
was present:
 
  USE="altivec"

This flag needs to be set as:

  CPU_FLAGS_PPC="altivec"

It's advised to keep 'altivec' USE flag enabled to ensure safe
migration and compatibility with external repositories.
'vsx', 'vsx2' and 'vsx3' are new flags and no migration necessary.

To help users enable the correct USE_EXPAND flags PPC support has been
added to app-portage/cpuid2cpuflags package:

  # emerge -1v >=app-portage/cpuid2cpuflags-9
  $ cpuid2cpuflags